Fish Microbiology and Quality Assurance

Unit 9 - Assurance and management quality of fish

9.1.2. Physical/mechanical/instrumental methods
The physical method of quality evaluation involves the use of mechanical devices or instruments for size grading fish and shellfish, separating males and females of certain fishes, and for measuring moisture and fat content, degree of spoilage, colour, defects, pH, firmness etc.

Measuring degree of spoilage
Degree of spoilage in most types of chilled whole fish is determined by measuring progressive and marked changes in the electrical properties of the skin and underlying tissue. The instruments developed on this principle are Torrymeter (TM) of UK, Intelectron Fish Tester (IFT) of Germany, and RT- Freshness Grader (RTFG) of Iceland.
These provide a meter reading that can be calibrated in terms of the degree of spoilage or the shelf life remaining before the fish is inedible. However, the readings shown by these instruments should be standardized for different species and for same species at different geographic locations due to the possible difference in the proximate composition of fish.

The clock and thermometer are the two most important and commonly used physical instruments in any processing industry for maintenance of quality by controlling the processing time and temperature.